Desvendando o complexo de espécies da abelha de fogo Oxytrigona tataira (Smith, 1863) (Hymenoptera, Apidae, Meliponini): uma abordagem integrativa

Abstract

Despite the crisis currently faced by taxonomy, with limited financial and human resources and a significant gap in the training of new taxonomists, thousands of species are described and named every year across the globe. Much of this progress is made possible thanks to the incorporation and integration of new technological tools into traditional descriptive taxonomic work. After more than 250 years of hegemonic use of morphological data, new methods and data for delimiting, discovering, and identifying species are now gaining considerable ground in the field of traditional taxonomy, including molecular, biogeographic, and ecological analyses, which are complementary to morphological ones. This approach is referred to as integrative taxonomy (a combination of different sources of evidence). The integrative approach is particularly useful in the study of biodiversity hotspots, such as various environments in tropical regions, as well as in the study of groups that are known to contain a high number of cryptic species, such as the eusocial stingless bees (Tribe Meliponini). One interesting case is that of the fire bee Oxytrigona tataira (Smith, 1863), which has the species O. cagafogo as its junior synonym. However, the researcher who proposed this synonymy did not mention the evidence that led to such a decision. Additionally, the original description of the species is quite brief, and the indication of the type locality is incomplete, mentioning only the country where the specimens were collected—in this case, Brazil. This species is considered by different taxonomists to be of complex taxonomy, of doubtful status, and in need of taxonomic re-evaluation. In this context, we used an integrative approach, combining morphological study, geometric wing morphometrics analysis, and species distribution modeling to reveal the true identity of Oxytrigona tataira. For the morphological study, 923 Oxytrigona specimens from 14 Brazilian states were examined. The lectotype of Trigona tataira Smith, 1863 (= O. tataira) was also examined. The type material of Trigona cagafogo Müller, 1874 (= O. cagafogo) could not be examined, as it is lost. However, we studied specimens collected in Blumenau, Santa Catarina, located approximately 40 km from the type locality of O. cagafogo, which is Itajaí, Santa Catarina. For the geometric wing morphometrics analysis, the right forewing of 10 workers from 47 sampled colonies was used, totaling 470 wings analyzed. For the species distribution modeling, occurrence records of all studied Oxytrigona specimens were used, totaling 106 unique occurrence records, and environmental variables were downloaded from online databases. All specimens examined in this study were sampled in locations where the natural occurrence of O. tataira and O. cagafogo has been reported in the literature. In the morphological study, we identified three distinct morphotypes. Morphotype 1 is restricted to the northern Northeast and northern Tocantins (recognized as part of the North region), occurring in the Caatinga and Cerrado phytogeographic domains and also in Atlantic Forest enclaves found in high-altitude humid forests in Ceará. Morphotype 2 is widely distributed in the Atlantic Forest domain, from the South of the country to the southern Northeast; however, in the states of Bahia and Minas Gerais, it extends into the Caatinga and Cerrado domains. Morphotype 3 occurs in the Southeast and South of the country, present in the Southeast in ecotone areas (Atlantic Forest - Cerrado), and in the South in Atlantic Forest areas. The results of the geometric wing morphometrics analysis (Canonical Variables Analysis, Mahalanobis Distance, and Discriminant Functions) support the morphological study, delimiting three groups (three morphotypes), as do the results of the species distribution modeling, despite a slight overlap between part of the niches of morphotype 1 and morphotype 2. Morphotype 1 corresponds to the species Oxytrigona tataira Smith (1863), whose studied specimens match perfectly with the description provided by Smith (1863) and also with the type specimen of Trigona tataira Smith, 1863, which is deposited at the BMNH. Morphotype 2 corresponds to the species Oxytrigona cagafogo (Müller, 1874), which consistently differs from O. tataira, and morphologically agrees perfectly with the description provided by Müller (1874), for which we propose the revalidation of its taxonomic status as a valid species. Morphotype 3 presents consistent differences from the other two and does not match the description of any formally described Oxytrigona species to date, and therefore, in this study, we propose it as a new species within the genus Oxytrigona.